Study On Application Of Cement Mixing Pile In Peat Soil Along Kunming Metro

Kunming Metro Line 3 starts from Xishan Park and ends at the East passenger transport center.Along the line,there are stations such as Chunyu Road station,Renmin West Road station,Dongfeng West Road station,Dongfeng East Road station and Taiping Road station,with a total length of 23 kilometers.Shizui depot is located in the Plateau Basin of East Yunnan,the soil of the site are mainly soft soil and artificial fill,and the peat soil layer is the most representative.In order to ensure the stability and safety of the foundation in Shizui depot,the cement mixing pile is designed to reinforce the soft soil in the depot.The peat soil in the study area is gray black,mainly plastic,loose in structure,mainly composed of incomplete decomposed plant debris,with low bulk density,high water content,high void ratio,strong compressibility and other characteristics,which has a great influence on the pile forming effect of cement mixing piles.The previous construction experience shows that the pile formed in this area is always in poor quality.A systematic test and numerical simulation study are carried out,in order to provide a reference for the design and construction of cement mixing pile in the construction site and similar engineering geological conditions.Firstly,the paper finds out the geological conditions of this area,summarizes the distribution characteristics and physical and mechanical properties of peat soil in Shizui depot,and puts forward the values of physical and mechanical parameters including water content,organic matter content and compression modulus.The compression test and direct shear test are carried out.By comparing the test results under different curing time and combining with the field construction effect,the main factors affecting the binding performance of peat soil and cement slurry are summarized,including the cement slurry mix ratio,curing age,admixture mixing ratio,etc.,and the recommended value is proposed.Through the numerical simulation technology of PLAXIS,the strengthening effect of cement mixing pile is studied,and the feasibility of the relevant parameter value proposal is verified.The results show that the pile parameters proposed in this paper can meet the requirements of surface settlement control in the study area.The results of this paper can solve the problem of poor pile forming effect of cement mixing pile in the peat soil layer of Kunming,especially provide good support and reference for the follow-up construction of Kunming Metro.